There is a desire to lower complexity and cost of radio frequency (RF) communications systems. The development and acquisition cost of an RF system is determined by the combination of the hardware, software, and firmware costs (material and engineering). However, the use of an RF system involves costs far beyond those incurred in the development and acquisition of an RF system. The integration of an RF system requires installation, power and cooling costs. Additionally, the ongoing use of the RF system requires operational costs to maintain system performance especially external antennas, which may need to endure environmental hazards. These costs continue to compound when multiple RF systems are used. As an example, an airborne vehicle may require the use of a radar, communications device, and electronic warfare (EW) system. The airborne platform in this example would host three RF systems and may require up to three antenna installations to support these systems. The use of the airborne platform would incur all the associated costs to acquire, install, and operate three RF systems. As RF antenna technology improves to cover wider frequency ranges with improved power efficiency, it is now possible to share an antenna between multiple RF systems. Sharing an RF antenna would reduce the overall number of antennas needed and directly reduce costs. In our example, one modern antenna may provide the frequency and power requirements needed for the airborne platform's Radar, communications device, and electronic warfare systems. This will reduce the acquisition costs of the RF systems some, but the largest cost savings are achieved from the reduction in power, cooling, and operational costs of using multiple RF systems. While advances in materials and manufacturing have led to modern antennas supporting multiple applications, the technology to utilize these modern antennas at timescales relevant to RF applications has lagged.
FIG. 1 is a simplified block diagram of a known digital RF transmit and receive system. As shown, one or more data processor (DP) cards 102 that include a processor, memory and associated I/O circuitry host general purpose application software. One or more signal processor (SP) cards 106 that include a processor (e.g., an image processor), memory and associated I/O circuitry typically contain signal processing software and firmware required to digitize received signals or synthesize signals for transmission. A system may have one to many SP cards 106 based on the capacity need of the system. A SP card (or module) may include a combination of digital signal processing circuits, software and firmware required to characterize the received RF signal or synthesize the RF signal for transmission. RF converters 108 shift analog signals in frequency either down or up to support receive and transmit modes, respectively. Amplifiers 110 and antennas 112 add additional power and directionality to the RF system both for receive and transmit modes.
As shown in FIG. 1, there is a one-to-one correspondence of SP cards 106 to RF converters 108, amplifiers 110, and antennas 112 (front end resources). Transmit and receive is scheduled by a scheduling routine 104 in the DP card 102. However, the resolution of the schedule is typically limited to around 100 milliseconds due to the computation time and latency of moving data from the DP through the system. This architecture has the benefit of a simple hardware design, where the number of SP cards would be sized based on the maximum expected number of concurrent system tasks. As an example, if each SP card 106 could process one task and the system was required to process 8 tasks simultaneously, the total number of required SP cards 106, RF converters 108, amplifiers 110 and antennas 112 would be 8.
FIG. 2 is a simplified block diagram of a known digital RF transmit and receive system. This illustrated hardware and software architecture introduces an RF distribution that may be hard-wired or configured by a programmable RF switch 209 to provide more dynamic routing between the RF converters 208 and the amplifiers 210 and antennas 212 (front end resources), utilizing a configurable routing routine 207. Here, the number of front end resources (m) is typically less than the number of SP cards 206 (n). The number of SP cards 206 (n) is based on the maximum expected number of concurrent system tasks. The number of front end resources (m) may be reduced to lower the cost of the system. The number of front end resources may be reduced to the maximum expected number of simultaneous tasks within a 100 ms period of time (the resolution of the scheduler 204). Extending the previous example of FIG. 1, if the system is required to accommodate up to 8 tasks over several minutes and the probability over a 100 ms window of time that tasks needed front end resources was:                Probability of 1 task needing front end resources=55%        Probability of 2 tasks needing front end resources=20%        Probability of 3 tasks needing front end resources=15%        Probability of 4 tasks needing front end resources=6%        Probability of 5 tasks needing front end resources=2.5%        Probability of 6 tasks needing front end resources=1.0%        Probability of 7 tasks needing front end resources=0.4%        Probability of 8 tasks needing front end resources=0.1%        
For example, a system may be designed with 8 SP cards 206 and 4 front end resources to provide sufficient resources for an anticipated 96% of system front end resources needs. In most cases, n>m. In the cases where the number of SP cards 206 (n) is greater than the number of front end resources (m), the DP 202 must provide resource arbitration 214 for the (4% of) requests that will require more front end resources than the system can provide.
However due to the resolution of the scheduler, these approaches typically lead to higher contention time and result in poor front end duty factor usage (e.g., resource dead time). Additionally, the complex RF distribution introduces cost and performance degradation to the system. The disclosed invention provides an improvement to the RF transmit and receive architecture to realize time sharing of front end resources to include RF antennas.